Cellulose-containing fabrics and process therefor



United States Patent 3,451,763 'CELLULOSE-CONTAININ G FABRICS AND PROCESS THEREFOR Ernst Weiss, Wattwil, Switzerland, assignor to Heherlein Patent Corporation, New York, N.Y., a corporation of New York No Drawing. Filed Mar. 6, 1964, Ser. No. 350,095 Claims priority, application fivgtzerland, Mar. 8, 1963,

Int. Cl. D06m 9/14 US. Cl. 8115.7 19 Claims This invention relates to a process for improving the properties of fabrics, and more particularly, to a process for improving the wetand dry-crease recovery properties of cellulose-containing fabrics while retaining high tensile strengths; and to the fabrics obtained by the process.

Cellulose-containing fabrics, especially cotton fabrics, can be made crease resistant by treating them with precondensates of artificial resins, or cross-linking agents, and then heating the chemically treated fabric to temperatures in the range of 130 to 180 C. in the presence of a catalyst. These compounds which confer crease resisttance on cellulose-containing textiles are known as crosslinking agents because it is believed that they react with the hydroxyl groups of the cellulose to form bridges, or links, between adjacent cellulose entities. Examples of these cross-linking agents for improving crease resistance are methylol compounds of urea and derivatives of urea and melamine.

Additionally, cellulose-containing fabrics may be impregnated with cross-linking agents such as dichloropropanol followed by treatment with alkali, or cross-linking agents such as formaldehyde, acetals, or methylol derivatives of nitrogen compounds, such as ethyleneurea, in a relatively strong acid solution may be applied to improve the wet-crease recovery properties of such fabrics. While these treatments improve the wet-crease recovery properties of the fabric, they have essentially no effect on the dry-crease recovery properties thereof.

In producing cellulose-containing fabrics, is is desirable that the material have resistance to creasing, or wrinkling, both when wet and when dry. The advantage of combining both wetand dry-crease resistance in a fabric is that it may, for example, be run through the spin-dry cycle of an automatic wash machine and then hung up to dry, whereas fabrics which do not combine both Wetand drycrease resistance must be hung up soaking wet if they are to dry without creases. Prior art processes producing both good wet and dry crease recovery, of which I am aware, are complicated and can, as a rule, not be carried out on regular finishing equipment.

It is possible to obtain both wetand dry-crease recov ery properties in cellulose-containing fabrics by impregnating them with solutions containing salts which cause cellulose to swell, in conjunction with :a cross-linking agent for cellulose; and heating the impregnated material to an elevated temperature. Thus, for example, impregnating a cellulose-containing fabric with a salt, such as zinc chloride or lithium bromide, to cause swelling and a cross-linking agent, such as dimethylol ethylene urea, and heating the material to temperatures of 100 to 150 C. produces both wetand dry-crease recovery properties in the cellulose-containing fabric. The disadvantage of this treatment, however, is that the tensile strength of the fabric is materially lessened.

I have conceived by my invention a process by which I am able to overcome the foregoing difficulties and disadvantages in the treatment of cellulose-containing fabrics so as to produce a fabric which has good wetand drycrease recovery properties, and to do so while maintaining a good tensile strength in the treated material.

Patented June 24, 1969 Thus, I contribute a cellulose-containing fabric and a process for producing such a fabric from which water can be extracted by spinning and which can then be hung for drying, whereby the creases during drying disappear.

An important aspect of my invention resides in a process which comprises impregnating a cellulose-containing fabric with an aqueous solution containing one or more salts which will cause the cellulose to swell and one or more cross-linking agents for cellulose; preferably removing excess solution from the fabric; heating the fabric to a temperature in the range of 60 to 140 C.; washing and drying the fabric which has been treated and subjected to the elevated temperature; impregnating the dried fabric with a second aqueous solution containing one or more cross-linking agents for cellulose; preferably removing excess solution from the fabric; subjecting the fabric to a temperature in excess of 130 C. and preferably of the order of 140 to 170 C.; and washing and drying the fabric. This treatment will impart good wetand drycrease recovery to the fabric and at the same time allow it to maintain good tensile strength. Prior to the second last treatment, the material may be dried at temperatures of 50 to C.

According to another important aspect of my invention, better tensile strength maintenance can be obtained in the fabric by treating it according to a process which comprises impregnating the material with an aqueous solution containing one or more salts which cause cellulose to swell and one or more cellulose cross-linking agents; removing any excess solution; subjecting the fabric to an elevated temperature in the range of from about 60 to about 140 C.; washing and drying the fabric; impregnating the dried fabric with another aqueous solution which contains one or more cross-linking agents for cellulose; subjecting the fabric to elevated temperatures above C., generally of the order of -170 C. and washing and drying the fabric, at least one of the curing steps being conducted with the fabric stretched to its original,

or raw, dimension lengthand/or fillingwise. Restoration of the original, or raw, dimension means that the fabric is subjected to such a high tension at least during predrying that it returns to its original length or width that is the length or width it had in its original, or raw, state. This preferred embodiment involving the use of high tension will result in the achievement of better tensile strength than when the fabric is dried under normal tension.

If desired, a catalyst may be used in conjunction with the cross-linking agents. Both of the two aqueous solutions, or impregnating baths, may contain either the same or different cross-linking agents. If desired, a combination of cross-linking agents may be used in each bath, so long as the agents are compatible.

As we have stated above, after the cellulose-containing fabric has been impregnated with the aqueous solution, the fabric must then be exposed to an elevated temperature. This exposure to elevated temperatures will also be called curing, and curing and exposure to elevated temperatures are used interchangeably and synonymously herein.

The elevated temperatures to which the fabric is exposed after the first impregnation bath are in a range from about 60 to about 140 C. for about 1 to about 10 minutes. After the second bath, the elevated temperature to which the fabric is exposed prefer-ably lies in the range to about 140 to C. for 1 to 10 minutes. Prior to the second heat treatment the textile material is preferably dried at temperatures ranging from 50 to 100 C. The curing required in the practice of this invention is effected by exposure of the impregnated fabric to elevated temperatures. Heated air, superheated steam, or other gases at the required temperatures are suitable.

Suitable cellulose swelling agents are metal salts which will form aqueous solutions. Zinc chloride, zinc thiocyanate, calcium chloride, potassium thiocyanate, lithium bromide and magnesium perchlorate are especially suited for use as swelling agents in this invention. These metal salts are preferably used in amounts of from about 5 to about 40% by weight of the treatment, or impregnation, bath. Unless otherwise indicated, all percentages given herein are on a weight basis.

Cellulose cross-linking agents are well known in the textile treatment art, and any cross-linking agents that react with cellulose to form cross-linkages at elevated temperatures with or without the addition of an acid or alkaline catalyst are suitable agents in the practice of this invention. Reactant resins, or precondensates, that is, compounds that form no resins or high polymers in the normal manner but do react with hydroxyl groups on the cellulose to form cross-linkages, may be used. Suitable cross-linking agents for cellulose are acetals, for example, reaction products of formaldehyde and diethyleneglycol; dimethylol monacarbamates, such as dimethylol methylcarbamate and dimethylol urea; cyclic dimethylol urea compounds, such as dimethylol compounds of ethylene urea or dioxyethylene urea; triazones such as 1,3-dimethylol-S-hydroxyethyl perhydrotriazone-Z; methylol melamine compounds, such as tetramethyl melamine and water-soluble etherified methylol melamine compounds; and epoxides such as the diglycidyl ether of ethylene glycol. Further suitable cross-linking agents are aldehydes, such as formaldehyde; glyoxal, and glutaraldehyde; epichlorohydrin; pyridinium compounds of chloromethyl ethers; divinylsulfono-derivatives; tris (l-aziridinylphosphinic oxide; and hexamethylene diethylene urea.

If desired, the usual acid or potentially-acid catalysts may be added to the two aforementioned treating baths. Examples of these catalysts are oxalic and citric acid, magnesium chloride, zinc fluoborate, magnesium perfiuoborate, diammonium sulfate, and zinc nitrate. Also suitable for use in the practice of this invention are alkaline catalysts such as sodium carbonate. As is known in the art, alkaline catalysts are used, for example, where divinylsulfono-derivatives are the cross-linking agents.

It has also been found desirable to apply commercial varieties of cationic or ketene fabric-softeners in conjunction with the process of this invention. Such softeners may be applied to the fabric before the first impregnation bath, after the second impregnation bath treatment, or in between the two impregnation baths. If desired, and if the cross-linking agents are compatible with the fabric-softener, fabric-softeners can be added directly to the treatment baths. In addition, finishing agents that give the goods a fuller and stiffer hand, such as polyvinyl alcohol, starch, or modified starch, may also be added to the second impregnation bath. It is further preferred to add a wetting agent, such as a nonionic polyoxethylene material, to the second impregnation, or treating, bath. After treatment in the second bath, the fabric may further be subjected to a calendering operation before or after the application of heat.

The process of this invention is useful in the treatment of all types of cellulose-containing fabrics, especially in the treatment of woven or knitted cellulose-containing materials such as cotton, or of regenerated cellulose materials such as rayon. It is further useful for materials made from cellulose derivatives and can be applied to the treatment of mixtures of fibers from natural and regenerated cellulose, and cellulose derivatives. Further, mixed fabrics made from cellulose or cellulose-containing materials togather with other natural or synthetic fibers can be treated by this process to obtain finished goods having wetand dry-crease recovery.

In connection with the preferred embodiment of this invention wherein the fabric is cured under high tension, the high tension may be applied during the heat treatment after either the first or second bath, or during the heat treatment following each of the two baths; but the best results are obtained when the fabric is cured under strong tension after both the first and the second impregnation treatments.

The tension of the fabric during heat treatment is preferably applied in the direction in which the fabric normally has the lower tensile strength. For example, the process of this invention is especially suited for the preparation of cotton shirting materials, and since these generally show a lower thread count, and hence lower tensile strength, in the filling direction than in the warp direction, the highe tension is applied in the filling direction.

The crease-resistance of the fabric is determined by a crease-angle measurement. The higher the crease angle recovered by the fabric, the greater is its resistance to creasing.

As used herein all dry-crease angle measurements were carried out in the following manner: Strips 5 centimeters long by 3 centimeters wide were cut with their longer dimensions on the grain of the fabric in either the warp or filling direction, and conditioned for twenty-four hours at 21 C. and 65% relative humidity. They were then placed on a clean microscope slide and one end of each sample was folded back 180 one centimeter from the end and squared to overlap the remainder of the sample. The samples were than covered with another microscope slide which was weighted down with a one kilogram weight and permitted to set for one hour.

After this step the samples were laid out on a glass sheet in an air conditioned room for fifteen minutes, and the angles formed between the folded portion of the sample with the remainder of the strip were measured. A number of strips were prepared in both the warp and the filling directions, and the mean of the angles in the two directions is reported as the mean crease angle.

The wet-crease angle was measured by placing the strips in water containing a wetting agent at room temperature for ten minutes. Excess water was then squeezed out with a wringer under light uniform pressure, and the samples were placed on microscope slides and subjected to the same procedure as in the case of measuring the dry-crease angle.

The following examples illustrate some embodiments of this invention, but are not to be considered as representing the entire scope of this invention.

EXAMPLE I The fabric employed was a cotton imitation poplin which was mercerized and bleached by the methods conventionally used in the art. Its weight and raw crease recovery properties are indicated by the following data:

No. of warp and filling ends per French inch 34 ends, 17 picks. English yarn count 40/1 in the warp, 30/1 in the filling. Average warp and filling drycrease angle 47. Average warp and filling wet-crease angle 63.

An aqueous solution containing a cellulose cross-linking agent and a salt which causes cellulose to swell was prepared by dissolving proportions of grams of 50% dimethylol ethylene urea (cross-linking agent) and 150 grams of zinc chloride powder (swelling agent) with one liter of water. The second aqueous solution was prepared by admixing grams Fixapret TN (trademark of Badische Anilinund Sodafabrik) triazone resin (crosslinking agent), 13 grams of magnesium chloride, and 1 gram of Triton X-lOO (trademark of Rohm & Haas Company, Philadelphia), iso-octyl phenyl polyoxethylene surface active agent with each liter of water.

The cotton polin fabric was impregnated with the aqueous solution of cross-linking agent and salt, squeezed to remove the excess solution, and exposed to hot air at 80 C. for four minutes under normal tension in both the warp and filling direction, washed in cold water, and dried under tension. After this first impregnation and curing, the fabric was impregnated with the second aqueous solution, squeezed under a high uniform load to remove excess solution, dried under light tension at 70- 80 C., cured at 150 C. for four minutes, washed in an aqueous solution containing 1 gram per liter of soda ash and 1 gram per liter of a fatty alcohol sulfate, rinsed in cold water and dried under normal tension.

The light tension used in this and other examples refers to a tension sufficient to keep the material taut, but not to restore it to its original, or raw, dimension.

After this treatment, the cotton poplin exhibited a dry crease angle of 135 and a wet crease angle of 142.

The squeezing referred to in Example I and other examples is a means of removing excess aqueous solution from the fabric. In general, in all of the examples the total pick-up of aqueous solution was about 8090% after the first aqueous solution and 70-75% after the second aqueous solution, both calculated on the weight of the air-dried fabric.

Comparable results are obtained on other woven or knitted fabrics made from natural cellulose, e.g., cotton, or on woven and knitted fabrics made from regenerated cellulose, cellulose derivatives and synthetic fibers in combinations with cotton.

EXAMPLE II An aqueous solution containing a cellulose cross-linking agent and a salt which causes cellulose to swell was prepared by dissolving -80 grams of 50% dimethylol dioxyethylene urea (cross-linking agent), 50 grams of zinc chloride powder (swelling agent), and 0.5 gram of concentrated acetic acid in each liter of water. A second aqueous solution was prepared by admixing r120 grams of Fixapret TN triazone resin (cross-linking agent), grams Catalyst PR (trademark of Ciba, Ltd., Basel, Switzerland) zinc nitrate catalyst, and 1 gram Triton X-100 surface active agent with each liter of water.

The cotton imitation poplin of Example I was impregnated with the aqueous solution of cross-linking agent and salt, cured at 100 C. for three minutes, washed in cold water, and dried under light tension. After this first impregnation and curing, the fabric was impregnated with the second aqueous solution containing cross-linking agent, squeezed to remove excess aqueous solution, dried under tension at 80 C., cured at 160 C. for three mintues, washed at 60 C. in an aqueous solution containing 1 gram/liter fatty alcohol sulfate and 1 gram/liter soda ash, rinsed and dried under light tension.

After the treatment of this example the dry-crease angle was 143 the wet crease angle, 142.

EXAMPLE III The first aqueous solution containing a cellulose crosslinking agent and a salt which causes cellulose to swell was prepared by admixing 120 grams of 50% dimethylol propylene urea (cross-linking agent), 100 grams of zinc chloride powder (swelling agent), and 0.25 gram concentrated acetic acid with each liter of water. The second aqueous solution was prepared by dissolving 100 grams of 50% dimethylol propylene urea (cross-linking agent), 10 grams Catalyst PR zinc nitrate catalyst, and 1 gram of Triton X-100 surface active agent in 1 liter of water.

The imitation cotton poplin of Example I was impregnated with the first aqueous solution, squeezed to remove the excess solution, subjected to an elevated temperature for 2 /2 minutes by passing hot air at 100 C. over the fabric, rinsed in cold water, and dried under light tension. After this first impregnation and exposure to elevated temperature, the fabric was impregnated with the second aqueous solution, squeezed to remove the excess moisture, dried at 70 C., exposed to an elevated temperature of 170 C. for 1.5 minutes, washed at 60 C.

in an aqueous solution prepared by dissolving 0.5 gram sodium carbonate and 1 gram Sandopan N (trademark of Sandoz, Basel, Switzerland) sulfonated castor oil-sulfated fatty alcohol synethetic detergent in each liter of water, rinsed in cold water and dried under light tension.

The dry-crease angle obtained was 153", and the wetcrease angle was 145.

EXAMPLE IV An aqueous solution containing a cellulose cross-linking agent and a salt which causes cellulose to swell was prepared by dissolving 140 grams of Quaker Reactant 53 (trademark of Quarker Chemical Products Corp, Conshohocken, Pa.) glycolpolyacetal and 250 grams zinc chloride powder (swelling agent) in each liter of water. A second aqueous solution was prepared by admixing 140 grams of 50% dimethylol methyl carbamate (crosslinking agent), 16 grams magnesium chloride crystals, and 1 gram Triton X surface active agent with each liter of water.

The cotton imitation poplin of Example I was impregnated with the aqueous solution of cross-linking agent and salt, squeezed to remove exces solution, subjected to an elevated temperature by passing hot air at C. over the fabric for 1 /2 minutes, washed off in cold water, scoured with a ten milliliter/liter solution of concentrated acetic acid, rinsed until a neutral reaction was obtained, and dried. After this first impregnation and curing, the fabric was impregnated with the second aqueous solution containing cellulose cross-linking agent, squeezed to remove excess aqueous solution, dried at 80 C., exposed to an elevated temperature of 160 C. for 2% minutes, washed at 70 C. in an aqueous solution containing 1 gram per liter of non-ionic synthetic detergent and 1 gram per liter of soda ash, rinsed in cold water, and dried under light tension.

After the treatment of this example the cotton poplin exhibited a dry-crease angle of 148 and a wet-crease angle of EXAMPLE V An aqueou solution containing a cellulose cross-linking agent and a salt which causes the cellulose to swell was prepared by admixing 150 grams of 50% dimethylol methyl carbamate (cross-linking agent), and 200 grams of zinc chloride powder (swelling agent) with each liter of water. The second aqueous solution containing a cellulose cross-linking agent was prepared by dissolving 70 grams of 50% dimethylol dioxyethylene urea (cross-linking agent), 10 grams Catalysator PR zinc nitrate catalyst, and 1 gram Triton X-100 surface active agent in each liter of water.

The cotton imitation poplin of Example I was impregnated with the aqueous solution of cross-linking agent and salt, squeezed to remove excess solution, cured by exposure to hot air at 100 C. for 4 minutes, washed in cold water, secured with very dilute acetic acid, rinsed until a neutral reaction was obtained, and dried under light tension. After this first impregnation and exposure to an elevated temperature, the fabric was impregnated with the second aqueous solution containing a cellulose crosslinking agent, squeezed to remove excess solution, dried at 70 C., cured at C. for 2.5 minutes, washed at 60 C. in an aqueous solution containing 1 gram/liter of fatty alcohol sulfate, rinsed in cold water, and dried under light tension.

After the treatment of this example the cotton fabric had a dry-crease angle of 148 and a wet-crease angle of 149.

EXAMPLE VI An aqueous solution containing a cellulose cross-linking agent and a salt which causes cellulose to swell was prepared by dissolving 100 grams of Lyofix CH (trademark of Ciba, Ltd., Basel, Switzerland) melamine formaldehyde precondensate (cellulose cross-linking agent), and 150 grams of zinc chloride powder (swelling agent) in each liter of water. A second aqueous solution containing a cellulose cross-linking agent, was prepared by admixing 80 grams of 50% dimethylol dioxethylene urea (crosslinking agent) grams of Zn(NO 6H O crystals and 1 gram of Triton X-lOO surface active agent with each liter of water.

The cotton imitation poplin of Example I was impregnated with the aqueous solution of cross-linking agent and swelling salt, squeezed to remove the excess aqueous solution, subjected to an elevated temperature of 80 C. by exposure to hot air for five minutes, washed thoroughly in cold water, and dried under light tension. After this first impregnation and curing, the fabric was impregnated with the second aqueous solution containing a cellulose cross-linking agent, dried at 80 C., cured at 170 C. for 1% minutes, washed in an aqueous solution containing 1 gram per liter of fatty alcohol sulfate, rinsed thoroughly and dried under light tension.

Upon testing after the treatment of this example, the cotton poplin exhibited a dry-crease angle of 153 and a wet-crease angle of 142.

EXAMPLE VII An aqueous solution containing a cellulose cross-linking agent and a salt which causes cellulose to swell was prepared by dissolving 60 grams of 38% formaldehyde (cross-linking agent) and 250 grams of zinc chloride pow der (swelling agent) in each liter of water. A second aqueous solution was prepared by admixing 150 grams of dimethylol methyl carbamate (cross-linking agent), 15 grams of magnesium chloride crystals, and 1 gram of Triton X-100 surface active agent with each liter of water.

The imitation cotton poplin of Example I was impregmated with the aqueous solution of cross-linking agent and salt, squeezed to remove excess solution, cured at 90 C. for 3 minutes by exposure to hot air at that temperature, washed with cold water, scoured in a cold bath containing 10 milliliters per liter of concentrated acetic acid, rinsed in cold water until a neutral reaction was obtained, and dried under light tension. After this first impregnation and curing, the fabric was impregnated with the second aqueous solution, .dried at 80 C., cured at 150 C. for 4 minutes, washed at 60 C. in an aqueous solution containing a surface active agent and soda ash, rinsed in cold water, and dried under light tension.

After the treatment of this example, the cotton poplin was found to exhibit a dry-crease angle of 127 and a wet-crease angle of 137.

EXAMPLE VIII An aqueous solution containing a cellulose cross-linking agent and a salt which causes cellulose to swell was prepared by dissolving 140 grams of 50% dimethylol ethylene urea (cross-linking agent), 350 grams CaSCN. 3H O crystals (swelling agent), and 14 grams of Catalyst PR zinc nitrate catalyst in each liter of water. A second aqueous solution containing a cross-linking agent was prepared by admixing 120 grams of 50% dimethylol methyl carbamate (cross-linking agent), 10 grams Catalyst PR zinc nitrate catalyst, and 1 liter of water.

The imitation cotton poplin of Example I was impregnated with the aqueous solution of cross-linking agent and salt, squeezed to remove excess water, cured by exposure to hot air at 60 C. for 8 minutes, rinsed in cold water, and dried under light tension. After this first impregnation and exposure to elevated temperature, the cotton poplin fabric was impregnated with a second aqueous solution, squeezed to remove excess solution, pre-dried at 90 C., cured at 160 C. for 2 minutes, washed at 70 C. in an aqueous solution containing 1 gram/liter of fatty alcohol sulfate and 1 gram/liter of soda, and dried.

After this treatment, the poplin was found to have 8 a dry-crease angle of 124 and a wet-crease angle of 132.

EXAMPLE dX An aqueous solution containing a cellulose cross-linking agent and a salt which causes cellulose to swell was prepared by admixing 160 grams of Fixapret TN triazone resin (cross-linking agent) and 150 grams of zinc thiocyanate with each liter of water. A second aqueous solution was prepared by dissolving grams of dimethylol dioxyethylene urea (cross-linking agent) and 10 grams of magnesium chloride crystals in 1 liter of water.

The cotton imitation poplin of Example I was impregnated with the aqueous solution of cross-linking agent and salt, squeezed to remove excess solution, cured at 110 C. for 3 minutes, rinsed in cold water, and dried under light tension. After this first imp regnation and exposure to elevated temperature, the fabric was impregnated with the second aqueous solution containing cross-linking agent, squeezed to remove any excess solution, dried at 90 C., exposed to an elevated temperature of 150 C. for 3 minutes, given a rinsing at 60 C. in an aqueous solution containing 1 gram/liter of fatty alcohol sulfate and 1 gram/liter of soda, rinsed in cold water, and dried under light tension.

After this treatment, the material was found to have a dry-crease angle of 122 and a wet-crease angle of 143.

EXAMPLE X An aqueous solution containing a cellulose cross-linking agent and a salt which causes cellulose to swell was prepared by dissolving 150 grams of lithium bromide (swelling agent), grams of tris (l-aziridinyl) phosphinic oxide (cross-linking agent), and 6 grams of zinc borofluoride catalyst in each liter of water. A second aqueous solution was prepared by admixing 100 grams of dimethylol propylene urea (cross-linking agent), 10 grams of magnesium chloride crystals and 1 gram of Triton X-100 surface active agent with each liter of water.

The cotton poplin of Example I was impregnated with the aqueous solution of cross-linking agent and salt, squeezed to remove excess solution, subjected to an elevated tempearture of 140 C. for 4 minutes, washed in cold water and dried under light tension. After this first impregnation and curing, the fabric was impregnated with a second aqueous solution, squeezed to remove any excess solution, cured at 150 C. for 4 minutes without any intermediate drying, washed at 60 C. in an aqueous solution containing 1 gram of surface active agent and 1 gram of soda ash per liter, rinsed in cold water, and dried under light tension.

After a treatment of this example the cotton poplin exhibited a dry-crease angle of and a wet-crease angle of 123.

As hereinabove disclosed, even better tensile strength maintenance can be obtained if the fabric is subjected to greatly increased tension during at least one of the curing steps of this invention. The amount of tension which is to be applied is sufficient to return the fabric to its original, or raw, dimension in the direction in which the increased tension is being applied. The following examples illustrate the practice of the process with such high tension and the additional benefits which accrue from this preferred embodiment of the invention.

EXAMPLE X-I An aqueous solution containing a cellulose cross-linking agent and a salt which causes cellulose to swell was prepared by mixing grams of a 50% solution of dimethylol methyl carbamate (cross-linking agent) and grams of zinc chloride crystals (swelling agent) with each liter of water. A second aqueous solution was prepared by dissolving .100 grams of Permafresh S W (trademark of Sun Chemical Corp.) triazone resin, grams of Catalyst vPR zinc nitrate catalyst, and 1 gram of Triton X-100 surface active agent in each liter of water.

A cotton poplin which differed from that of Example I only in its wetand dry-crease angles (as set forth hereafter) was impregnated with the aqueous solution of cross-linking agent and salt. One sample of the impregnated material was cured at 125 C. for one minute under high tension to maintain essentially the original dimension in the filling direction, and the other sample was cured under the same conditions except that only light tension was used. Both samples were then washed in cold water and dried under light tension.

Each of these two samples was impregnated after the first impregnation-and-curing step with the second aqueous solution and were squeezed to remove the excess of the second impregnating solution. The sample which was cured under light tension after the first bath was dried at '80" C. under light tension, cured at 160 C. for 2 minutes, washed at 60 C. with a solution containing 1 gram per liter of fatty alcohol sulfate and 1 gram per liter of soda, rinsed with cold water, and dried under light tension.

Of the material which had previously been cured under high tension, one portion was treated in the same manner as the just-described sample after the second bath, while the other portion was exposed to high tension in the direction of the filling during the curing.

The crease angles and the tensile strength of each sample were then determined, and the following data were obtained.

As can be noted from the foregoing data, while the crease angles are very slightly diminished for the samples which were cured under high tension, the tensile strength of the fabric is substantially improved in comparison to that cured under light tension.

Comparable results are obtained with mixed fabrics, woven or knitted, made from natural cellulose, e.g. cotton mixed with other natural and/or synthetic fibers.

The further additional examples illustrate some various combinations of light and high tension during curing, which make it possible to secure higher tensile strength while at the same time reaching relatively high crease angles. By the term high tension in these examples, I refer to a tension sutficient to maintain substantially the original dimensions in the indicated direction.

EXAMPLE XII An aqueous solution containing a cellulose crosslinking agent and a salt which causes cellulose to swell was prepared by adding 70 grams of 38% formaldehyde (crosslinking agent) and 200 grams of zinc chloride crystals to each liter of water. A second aqueous solution of crosslinking agent was prepared by admixing 120 grams of a 50% solution of dimethylol propylene urea (cross-linking agent), 12 grams of a zinc nitrate catalyst, and 1 gram of Triton X-100 surface active agent to each liter of water.

The cotton poplin of Example XI was impregnated with an aqueous solution of cross-linking agent and swelling salt, squeezed to remove excess solution and cured under high tension across the width of the unbleached fabric for 3 minutes at 100 C., thoroughly washed with cold water, and dried under light tension. In the second stage, the fabric was impregnated with the second aqueous solution, pre-dried under light tension at C., cured at 150 C. for a period of 4 minutes, washed briefly with a solution containing 1 gram per liter of fatty alcohol sulfate and 1 gram per liter of soda at 60 C., rinsed with warm and then with cold water, and dried under light tension.

A sample of the same fabric was then subjected to the same treatment, except that it was not cured under high tension. The material cured under light tension exhibited a dry-crease angle of 143, a wet-crease angle of 138, and a tensile strength in the filling direction of 9.8 kilograms, while the sample of the material which was dried under high tension in the first pre-treatment stage exhibited a dry-crease angle of 146, a wet-crease angle of 136 and tensile strength in the filling direction of 10.3 kilograms.

EXAMPLE XIII An aqueous solution containing a cellulose cross-linking agent and a salt which causes cellulose to swell was prepared by adding 150 grams of a 50% solution of dimethylol dioxyethylene urea and 150 grams of zinc chloride crystals (swelling agent) for each liter of water. A second aqueous solution was prepared by admixing grams of a 50% solution of dimethylol methyl carbamate (cross-linking agent), 10 grams of a Zinc nitrate catalyst, and 1 .gram of Triton X-lOO surface active agent to 1 liter of water.

The material of Example XI was impregnated with the aqueous solution of cross-linking agent and salt, and treated as in Example XII, except that the curing took place at C. for 75 seconds under high tension to maintain the fiber at its original dimension in the width of the unbleached fabric, and the fabric was predried under light tension at 80 C. and cured for five minutes at C. in the second impregnation-curing step.

The same material was treated under the same conditions except it was not exposed to high tension in the first stage.

The material cured under light tension was found to have a dry-crease angle of 159, a wet-crease angle of 159 and a tensile strength in the filling direction of 6.4 kilograms, whereas the material treated under increased tension had a dry-crease angle of 156, a wetcrease angle of 144 and a tensile strength in the filling direction of 12.2 kilograms.

EXAMPLE XIV An aqueous solution containing a cellulose cross-linking agent and a salt which causes cellulose to swell is prepared by dissolving 140 grams of Quaker Reactant 53 glycol polyacetal cross-linking agent and 180 grams of zinc chloride crystals (swelling agent) in each liter of water. A second aqueous solution containing a cross-linking agent was prepared by mixing 80 grams of Fixapret TN triazone resin (cross-linking agent), 10 grams of magnesium chloride crystals, and 1 gram of Triton X- 100 to each liter of water.

The fabric of Example XI was then treated as in Example XII, except that after the first impregnation the material was cured under light tension for three minutes at 100 C., washed with cold water, and dried under light tension, and in the second stage the material was predried at 70 C. under high tension in the filling direction, and then cured at C. for 1 /2 minutes.

A sample of the identical material was treated under the same conditions, except that all of the curing took place at light tension which did not maintain the original dimension of the material in the direction of the tension.

The material treated under light tension exhibited a dry-crease angle of 120, a wet-crease angle of 134, and a tensile strength in the filling direction of 13.3 kilograms, whereas the material cured under high tension in second stage had a dry-crease angle of 118, a wet-crease angle of 128, and a tensile strength in the filling direction of 15.7 kilograms.

EXAMPLE XV An aqueous solution containing a cellulose cross-linking agent and a salt which causes cellulose to swell was prepared by dissolving 100 grams of a 50% solution of dimethylol methyl carbamate cross-linking agent, 50 grams of a 28% solution of concentrated formaldehyde cross-linking agent, and 200 grams of zinc chloride (swelling agent) in each liter of water. A second aqueous solution containing a cross-linking agent was prepared by admixing 130 grams of Quaker Reactant 16 modified glycol-acetal cross-linking agent and 13 grams of magnesium chloride crystals with each liter of water.

The treatment of Example XIV was repeated except that curing took place under normal tension for two minutes at 100 C. after the first impregnation and the material was predried at 70 C. under high tension in the filling direction and was then cured for two minutes under high tension at 160 C. following the second impregnation.

A sample of the same material was treated in the same manner, except that it was dried and cured under light tension after the second impregnation bath.

The material cured under light tension in both stages showed a dry-crease angle of 95, a wet-crease angle of 121, and a tensile strength in the filling direction of 16.7 kilograms; whereas the material dried under greatly increased tension in the second stage exhibited a drycrease angle of 87, a wet-crease angle of 123 and a tensile strength in the filling direction of 19.9 kilograms.

EXAMPLE XVI An aqueous solution containing a cellulose cross-linking agent and a salt which causes cellulose to swell was prepared by admixing 140 grams of a 50% solution of dimethylol ethylene urea cross-linking agent and 150 grams of zinc chloride (swelling agent) with each liter of water. A second aqueous solution was prepared by admixing 90 grams of a 50% solution dimethylol dioxyethylene urea, grams of zinc nitrate crystals, and 1 gram of Triton X-l00 surface active agent with each liter of water.

The material of Example XI was impregnated with the aqueous solution of cross-linking agent and salt, stretched in the direction of the filling to nearly the width of the unbleached fabric (that is, under high tension), cured for 1.5 minutes at 120 C., thoroughly rinsed in cold water, dried under light tension and then impregnated with the second aqueous solution. After this impregnation it was dried at 80 C. under high tension, cured for three minutes at 160 C., and then washed, rinsed, and dried as in Example XII. A sample of the same material was treated in the same manner, except that it was cured and dried under only light tension.

The material cured under light tension exhibited a dry crease angle of 158, a wet-crease angle of 151, and a tensile strength in the filling direction of 7.9 kilograms; whereas the material dried under high tension after both impregnation steps had a dry-crease angle of 155, a wetcrease angle of 147, and a tensile strength in the filling direction of 13.1 kilograms.

EXAMPLE XVII An aqueous solution containing a cellulose cross-linking agent and a salt which causes cellulose to swell was prepared by dissolving 100 grams of Lyofix CH melamine-formaldehyde precondensate (cross-linking agent) and 180 grams of zinc chloride crystals (swelling agent) to each liter of water. A second aqueous solution was prepared by mixing 110 grams of Permafresh SW triazone resin cross-linking agent, 11 grams of a zinc nitrate catalyst and 1 gram of Triton X- for each liter of water.

The procedure of Example XVI was repeated but for the two aforementioned aqueous solutions, the curing after the first impregnation taking place 2 /2 minutes at 100 C., the drying after the second impregnation taking place at 80 C., and the curing after the second impregnation taking place at 145 C. for four minutes.

The process of this example was repeated on an identical fabric which was cured and dried under light, rather than high, tension.

After treatment the material which was cured under light tension was found to have a dry-crease angle of a wet-crease angle of and a tensile strength in the filling direction of 12.6 kg.; whereas the material cured under high tension exhibited a dry-crease angle of 133, a wet-crease angle of 133, and a tensile direction in the filling direction of 20.9 kg.

I believe that the practice of my novel process and the compositions of the fabric formed thereby will now be understood and that the advantages of my invention will be fully appreciated by those persons skilled in the art.

What I claim is:

1. A process for producing a fabric with high wetand dry-crease recovery angles which comprises impregnating a cellulose-containing fabric with a first aqueous solution containing at least one cellulose cross-linking agent and at least one salt which causes cellulose to swell, said salt being selected from the group consisting of zinc chloride, zinc thiocyanate, potassium thiocyanate, and lithium bromide in an amount at least about 5% by weight, curing said fabric at a temperature in the range of from about 60 to about 140 C., washing and drying said fabric, impregnating the dried fabric with a second aqueous solution containing at least one cellulose crosslinking agent, curing said fabric at a temperature of at least about 130 C., and washing and drying said fabric.

2. The fabric produced by the process of claim 1.

3. A process for producing a fabric with high Wetand dry-crease recovery angles which comprises impregnating a cellulose-containing fabric with a first aqueous solution containing at least one cellulose cross-linking agent and at least one salt which causes cellulose to swell, said salt being selected from the group consisting of zinc chloride, zinc thiocyanate, potassium thiocyanate, and lithium bromide in an amount at least about 5%, by weight, curing said fabric at a temperature in the range of from about 60 to about 140 C. for from about 1 to about 10 minutes, washing and drying said fabric, impregnating the dry fabric with a second aqueous solution containing at least one cellulose cross-linking agent, curing said fabric at a temperature of from about 140 to about C. for from about 1 to about 10 minutes, and washing and drying said fabric.

4. The process of claim 3 wherein the fabric is dried at a temperature in the range of from about 50 to about 100 C. after the fabric has been impregnated with the second aqueous solution and prior to the second curing of said fabric.

5. The process of claim 4 wherein the cellulose crosslinking agent is chosen from the group consisting of acetals, dimethylol monocarbamates, cyclic dimethylol urea compounds, triazones, methylol melamine compounds, epoxides, aldehydes, epichlorohydrin, pyridinium compounds of chloromethyl ethers, divinylsulfonoderivatives, tris (l-aziridinyl) phosphinic oxide, and hexamethylene diethylene urea, and the salt which causes cellulose to swell is chosen from the group consisting of zinc chloride, zinc thiocyanate, calcium chloride, potassium thiocyanate, lithium bromide, and magnesium perchlorate.

6. The process of claim 5 in which the first aqueous solution contains from about 5 to about 40% of the salt which causes cellulose to swell.

7. The process of claim 4 wherein both aqueous solutions contain the same cellulose cross-linking agent.

8. The process of claim 4 in which each of the two aqueous solutions contains a different cellulose crosslinking agent.

9. The process of claim 5 wherein the cellulose crosslinking agent is dimethylol methylcarbamate.

10. The process of claim 5 wherein the cellulose crosslinking agent is a triazone resin.

11. The process of claim 5 wherein the cellulose crosslinking agent is dimethylol ethylene urea.

12. A process for producing a fabric with high wetand dry-crease recovery angles, which comprises impregnating a cellulose-containing fabric with an aqueous solution containing at least one cellulose cross-linking agent and at least one salt which causes cellulose to swell, said salt being selected from the group consisting of zinc chloride, zinc thiocyanate, potassium thiocyanate, and lithium bromide in an amount at least about 5% by weight, curing said fabric at a temperature in the range of from about 60 to about 140 C., washing and drying said fabric, impregnating the dried fabric with an aqueous solution containing at least one cellulose cross-linking agent, drying said fabric, curing said fabric at a temperature above about 130 C. and washing and drying said fabric, at least one of the curing steps being conducted with said fabric being stretched to substantially its original dimensions in at least one direction.

13. The cellulose-containing fabric produced by the process of claim 12.

14. A process for producing a fabric with high wetand dry-crease recovery angles, which comprises impregnating a cellulose-containing fabric with an aqueous solution containing at least one cellulose cross-linking agent and at least one metal salt which causes cellulose to swell, said salt being selected from the group consisting of zinc chloride, zinc thiocyanate, potassium thiocyanate, and lithium bromide in an amount at least about 5% by weight, curing said fabric at a temperature in the range of from about 80 to about 130 C., washing and drying said fabric under tension, impregnating the dried fabric 'with an aqueous solution containing at least one cellulose cross-linking agent, drying said fabric, curing said fabric at a temperature in the range of from about 130 to about 180 C., and washing and drying said fabric, at least one of the curing steps being conducted with the fabric being stretched to substantially its original dimensions in at least one direction.

15. The process of claim 14 wherein the stretching is applied to the fabric before or during the curing step after the first impregnation.

16. The process of claim 14 wherein the stretching is applied to the fabric before or during the curing step after the second impregnation.

17. A process for producing a fabric with high wetand dry-crease recovery angles, which comprises impregnating a cellulose-containing fabric with an aqueous solution containing a cellulose cross-linking agent and a metal salt which causes cellulose to swell, removing excess aqueous solution from the fabric, curing said fabric at a temperature in the range of from about to about C., washing and drying said fabric under tension, impregnating the dried fabric with an aqueous solution containing a cellulose cross-linking agent, removing excess aqueous solution from said fabric, drying said fabric, curing said fabric at a temperature in the range of from about 130 to about C., and Washing and drying said fabric, both of the curing steps being conducted with the fabric being stretched to at least substantially its original dimensions in at least one direction.

18. The process of claim 17 wherein the stretching is applied in the direction of lower tensile strength of the fabric.

19. The process of claim 17 wherein the stretching is applied in the filling direction of the fabric.

References Cited UNITED STATES PATENTS 2,205,120 6/ 1940 Heberlein et al. 8-1l6.4 2,512,195 6/1950 Bener 8-116.3 2,977,665 4/1961 McElrath 8-116.3 3,094,372 6/1963 Hibbert et a1 8-l16.4 3,175,874 3/1965 Gagarine 8-12O 3,175,875 3/1965 Gagarine 8-ll6 X 3,189,404 6/ 1965 Takizaki et a1. 8-120 X 3,265,463 8/1966 Barber et al. 8--116.4

FOREIGN PATENTS 568,258 3/1945 Great Britain.

696,282 8/1953 Great Britain.

866,387 4/1961 Great Britain.

OTHER REFERENCES Reeves et al.: American Dyestulf Reporter, pp. 639- 644, Sept. 5, 1960.

NORMAN G. TORCHIN, Primary Examiner. I. CANNON, Assistant Examiner.

U.S.Cl.X.R. 

1. A PROCESS FOR PRODUCING A FABRIC WITH HIGH WETAND FRY-CREASE RECOVERY ANGLES WHICH COMPRISES IMPREGNATING A CELLULOSE-CONTAINING FABRIC WITH A FIRST AQUEOUS SOLUTION CONTAINING AT LEAST ONE CELLULOSE CROSS-LINKING AGENT AND AT LEAST ONE SALT WHICH CAUSES CELLULOSE TO SWELL, SAID SALT BEING SELECTED FROM THE GROUP CONSISTING OF ZINC CHLORIDE, ZINC THIOCYANATE, POTASSIUM THIOCYANATE, AND LITHIUM BROMIDE IN AN AMOUNT AT LEAST ABOUT 5% BY WEIGHT, CURING SAID FABRIC AT A TEMPERATURE IN THE RANGE OF FROM ABOUT 60* TO ABOUT 140*C., WASHING AND DRYING SAID FABRIC, IMPREGNATING THE DRIED FABRIC WITH A SECOND AQUEOUS SOLUTION CONTAINING AT ELAST ONE CELLULOSE CROSSLINKING AGENT, CURING SAID FABRIC AT A TEMPERATURE OF AT LEAST ABOUT 130*C., AND WASHING AND DRYING SAID FABRIC. 